This research plan proposes to test three hypotheses: Specific Aim 1: Expression of AgOr1 is restricted to the olfactory organs in the mosquito and is expressed in a stereotypic manner across individuals. I propose to expand our previous data showing olfactory tissue-specific RNA expression of agOr1 (see appendix) by using in situ hybridization (ISH). In addition Western blotting and immunohistochemistry (IHC) will be used to determined protein localization. ISH and IHC will be used to determine AgOr1 localization at the level of sensilla and olfactory receptor neurons (ORNs)> Developmental expression of AgOr1 will also be examined. Specific Aim 2: Expression of AgOr1 is under circadian control. The temporal expression patterns of AgOr1 will be examined in mosquitoes reared, maintained, and collected under specific light conditions. RT- PCR and ISH will be employed to investigate the RNA expression levels of AgOr1 at specific time points. Furthermore, protein levels of AgOr1 will be examined using Western blotting and IHC. Specific Aim 3: Expression of AgOr1 is down-regulated following a blood meal. Initial studies from our lab indicate that RNA levels of AgOr1 is down-regulated after a blood meal (see appendix). Quantitative RNA assays, such as ribonuclease protection assays, will be employed to more rigorously analyze this phenomenon under several blood feeding protocols.